Due to the critical role of insulin-like growth factor-1 (IGF-1) in development and survival of cells in the mammalian central nervous system (CNS), this protein has been considered a potentially important therapeutic agent for various conditions affecting the CNS. Delivery of IGF-1 by some methods, including viral vectors and intrathecal injection, has shown promise for treatment of ALS in animal models. However, subcutaneous administration of mature recombinant IGF-1 to human patients in clinical trials did not demonstrate efficacy in the treatment of ALS. Thus, there exists a need for improved methods of delivering a therapeutically effective amount of IGF-1 to a site of neuronal cell loss.